1. Field of the Invention
This invention relates generally to a method and device using a targeted light source and a photosensitizer to streamline the process of repairing internal body passageways, prevent restenosis, and minimize re-injury after angioplasty treatment.
2. Invention Disclosure Statement
The most common problem with any angioplasty procedure is restenosis, a re-closing of the affected passageway opened by the procedure. This effect is believed to be due to cell proliferation, triggered by the exerted pressure and the lesion caused by the balloon angioplasty. Restenosis occurs in about 30% of patients. The use of stents, or tiny expanding metal scaffolds, is the most common method used to prevent restenosis. However, restenosis through the stent or around the stented area is quite common.
Constrictions in the coronary artery are caused by a buildup of plaque. Plaque can occur in many forms, from a thick viscous consistency (similar to toothpaste) to a rock-hard consistency depending on the proportion of components, which may include calcium, fibrous tissue, fatty deposits, organized clots and thrombus.
Atherosclerosis is a common problem among humans. Fatty substances (lipids), or plaques, form deposits in and beneath the intima—the innermost membrane lining arteries and veins. Atherosclerosis commonly affects large and medium sized arteries. Most commonly affected are the aorta, and the iliac, femoral, coronary, and cerebral arteries. Health problems result from atherosclerosis when reduced blood flow due to constriction of one of the passageways restricts blood flow to a particular tissue or organ. Restricted blood flow compromises and restricts organ or tissue function.
Approximately four million people in the United States suffer from artherosclerotic coronary artery disease. Many of these people are likely to suffer or die from myocardial infarction, commonly known as heart attack. Heart disease is, in fact, the leading cause of death in the United States. Thrombosis in the coronary artery beyond the artherosclerotic constriction is the usual cause of heart attacks. A procedure that can open artherosclerotic constrictions thereby permitting the normal flow of blood to the heart can reduce many deaths and disabilities caused by heart disease.
Modern treatment of atherosclerotic blood passageways usually involves one of two treatments: bypass and/or angioplasty. In bypass treatment, a portion of a blood passageway is borrowed from another area in the body and grafted around the affected passageway. This treatment involves invasive surgery, especially when dealing with the aorta, coronary artery, or other vessels involving the heart. Furthermore, bypass surgery does not heal the affected site, and occurrences of atherosclerosis in the grafted passage are relatively common.
Another method of treating atherosclerosis is angioplasty. In angioplasty, a catheter of some sort is introduced into the passageway. In most methods, the angioplasty catheter, usually equipped with a guidewire, moves along the body passageway to the sclerotized area. A balloon contained inside of the catheter inflates, displacing the plaque and re-opening the passageway.
In another use of the prior art, a photosensitizer is introduced at the sclerotized area prior to introduction of the catheter. After time for the photosensitizer to target and saturate the sclerotized area, a catheter is introduced into the body passageway. Fibers are then inserted into the catheter. The fibers conduct light from some kind of source, i.e. a laser. The laser or other light source activates the photosensitizer in the sclerotized area in order to destroy the plaque. A balloon may or may not be used in this approach to further treat the sclerotized area of the blood passageway. This form of angioplasty is called Photodynamic Therapy (PDT), or intracoronary brachytherapy.
The photoactivating device employed for intracoronary brachytherapy usually comprises a monochromatic light source such as a laser, the light output of which may be coupled to an invasive light delivery catheter for conduction and delivery to a remote target tissue. Such interventional light delivery catheters are well known in the art and are described, for example, in U.S. Pat. No. 4,512,762 (Spears). In that invention a balloon is illuminated to activate the photosensitizer.
Generally, the prior art of intracoronary brachytherapy involves at least five steps: insertion of a guidewire; insertion of a catheter over the guidewire; removal of the guidewire; insertion of a fiberoptic wire; and finally, irradiation. The present invention is a method to prevent restenosis by using a novel catheter with light conducting means and a targeting mechanism for focusing that light source on a photosensitizer to treat a sclerotized area of a human body passageway. Most balloon angioplasty procedures do not involve radiation to prevent cell growth in the intima. Instead, they aim to compress or displace cells in a sclerotized vessel with a stent or other means. These treatments tend to encourage restenosis by stimulating a responsive force in the vessel wall, or stimulating the proliferation of cells in the area to re-take its original shape.
The present invention provides a non-mechanical method and product for preventing restenosis by irradiation. A “fiberoptic guidewire” assists the doctor or technician in navigating body passageways, and also conducts radiation to its own diffuser to engage in PDT. Alternatively, a balloon catheter is manufactured to conduct radiation to an obstructed body passageway. Either embodiment streamlines the angioplasty procedure.